Ignition system



ocf. 4, 1949.

IGNITION SYSTEM Original Filed Oct. 17, 1944 12- fw-l u IIIIIIIIIIIIIIIIIII y Me/vH/e F.' Peters F n 6 o Y /Ig INvENToR M. F. PETERS 2,483,428

v .Patented Oct. 4, 1949 IGNITION SYSTEM Melville F. peters, East orange, N. J. Continuation of application Serial No.' 559,107,

October 17,

1948, Serial No. 34,230

6 Claims. (Cl. 12S-148) (Granted under the act of March 3, 1883, as

amended-April 30, 1928; 370

This invention relates to improvements in electrical ignition systems for internal combustion engines. It provides an improved apparatus for pressurizing the ignition harnessv and spark plugs thereof in the case of aviation engines, and has utility in thelcase of such engines which are subjected only to normal atmosphericconditions.-

The increasingly high altitudes to which aircraft are being flown has caused shortk circ-uiting between the ends of the ignition cables and the spark generator, and between the said ends and grounded `parts of the harness such as that part of the shielded portion of the spark plug where the ignition wire contacts the central electrode of the spark plug. As is well known, it has become common practice to pressurize the radio shielding so that the ignition wires and insulation therein as well as thev spark plugs and magneto are maintained at a pressure a'bove the ambient pressure, thereby eliminating the aforementioned failure at high altitudes. However, a leak or break in the airtight radio shielding, such as caused by vibration or gun fire, eventhough it may not rupture the ignition cable, will cause ignition failure at high altitudes due to the loss of pressure.

' In many present installations such as in ordinary motor vehicles which may 'at times be required to operate in deep fords or the like whereby the engine or parts thereof may be partially under water, the ignition systems, including the cables leading to the spark plugs have been totally enclosed and sealed in a watertight manner. Due tothe fact that spark plugs will frequently leak gases from the combustion chamber past the central electrode, they build up a pressure where the ignition cables are attached, and the ignition lcables will frequently be damaged or destroyed.

This invention provides an apparatus whereby the ignition cables in the case of airplane engines are pressurized in such a manner that the radio shielding, if used, need not be made airtight, and whereby the spark plug itself is pressurized where the ignition cable contacts the central electrode thereof, and whereby short circuiting .between the cable shield of the plug and the ignition cable and electrode therein is'prevented.

The apparatus in either case involves the use of an ignition cable having a continuous longitudinal passageway therein within the central insulation. In the case of aircraft engine systems,

the radio shielding manifold or housing or other o particularly, the conductor may advantageously lie within this passageway, and the passageway provides a chamber which is pressurized so that the conductor itself may -be maintained at the 1944. This application June 21,

required atmospheric pressure, irrespective of the altitude at which the enginegmight be used. The cable is sealed to the spark plug in such a manner that air pressure within the passageway of the ignition ca'ble is applied to the interior portion of the spark plug within the tubular radio shield. Thus the ignition cable conductor and the interior of the spark plug as well as the magneto are maintained at the required pressure. Where the engine on which the cable is used has the ignition system sealed to prevent the entrance of moisture therein, as when operating under water, the central passageway in the ignition cable insulation lprovides an exit for gases which leak past the central electrode from the combustion chamber' and which would otherwise blow open the means by which the ignition cable is sealed to the spark plus.

This application isla continuation of Application Serial No. 559,107, filed October 17, 1944, for Ignition systems, now abandoned.

It is therefore a primary object of this invention to provide an improved apparatus for pressurizing the ignition system of an internal com' bustion engine to prevent failure due to short cincuiting at low atmospheric pressures.

Another object of this invention is the provision of an improved apparatus for pressurizing radio shielded spark plugs so as to prevent short circuiting between their central electrode or the ignition wire therein and the grounded tubular portion of the spark plug at low atmospheric pressures.

Another important object of lmy invention lis the provision of an apparatus whereby the leakage combustion gases which would otherwise increase the pressure to such an extent as to damage the seal of waterproofed ignition systems may be vented oi.

Another object of my invention is the provision of a novel hollow insulated ignition cable particularly adaptable for use in pressurized aviation ignition systems and in Awaterlproofed installations.

Other objects will become apparent Aas the description proceeds in connection with the drawings wherein: i

Fig. 1 is a side elevation, partly in section, of a detachable radio shielding ignition cable lead particularly adapted for aviation use, together with a spark plug to which it is attached, illustrating one species of hollow insulated and shielded ignition cable embodying my invention.

Figs. 2 to 6 are partial sectional views of other species of the ignition cable embodying my invention.

As shown in Fig. 1 a spark plug III has a tubular radio shield II to which is attached an elbow I2. A nut I3 secures the elbow to the top of the radio shield in the conventional manner. At the end of the elbow is a exible metallic radio shielding element comprising a corrugated metallic tube Il surrounded by a metallic braid I5. The other end of the metallic tube has a ange, not shown, against which the nut I6 bears to secure that end of the exible lead to the manifold of the metallic radio shield which carries the other ignition cables.

A ilexible element I1 of rubber or the like protrudes from the manifold end of ,the lead and connects to an ignition cable within the aforesaid manifold. The flexible tube, braid, element I1, and nut I6 are conventional and well known. In the embodiment illustrated in Fig. l, the conductor of the ignition cable comprises a conducting a wire I8 helically wound around a. ilexible tubular body I9. The tubular body I9 is advantageously of electrically conducting rubber or the like, whereby the electrical stress in the surrounding insulation is reduced, as disclosed in my U. S. Patent No. 2,322,773, issued June 29, 1943, and the conducting wire I8 may have the characteristics disclosed in said patent. The tubular body and Wire are centrally disposed within the flexible element I1, the flexible tube I4, the elbow I2, and the radio shield II. The space between the wire I8 and body I9 is sealed with a suitable high tension insulation material 29 which is plastic or flexible so that it will not break with exure. Within the shield II of the spark plug is located an insulating cigarette 20. An insulating bushing 2| lies within the cigarette and has an interior ilange 22. The tubular body I9 terminates adjacent the ange 22, and the spirally wound wire I8 is electrically bonded to a metallic contact 23 which is held by the ilange 22. A spring 24 contacts both the contact-23 and the top of the central electrode 25. The plastic or flexible insulation material 29 which centralizes the wire I8 continues down to the top of the contact 23 as shown in Fig. 1. Within the hollow body I9 the passageway 26 provides a means for applying pressure to the portion of the spark plug within the radio shield II. It should be noted that the passageway 2S extends all the way to the end of the flexible element I1 and through the conventional meta1 contact 21 at its end. Said passageway communicates with the interior of the shield II through a central passageway 28 in the contact 23. At its other end, the passageway communicates with a similar passageway in the cable leading to the magneto which is also pressurized. Thus the system from the magneto to the spark plug is pressurized. Since there is no potential gradient within the helical conductor the pressurized air within the passagewaywill not become ionized.

In` the embodiment of Fig. 2 the helical wire 3I is moulded within the hollow body 32 which may be of conducting rubber or the like having a central passageway 33. In all other respects this embodiment is the same as that shown in Fig. 1.

In Fig. 3 the helical wire 35 lies within the central passageway 36 of the hollow body 31 which may also be of conducting rubber or the like. The embodiment of Fig. 4 is similar to that of Fig. 3 except that the conductor 39 is straight instead of helical as is the wire 3i oi Fig. 3.

the embodiment of Fig. 5 the conductor 4l is similar to the helical wire Il oi Fig. 3 except that its coils are closely wound without any spacing therebetween, thus forming a single passageway 4I within the coil of wire.

In Fig. 6 the conductor comprises a braid of metallic strands and nonconducting strands. The braid may be impregnated with conducting rubber or the like. As clearly shown in Fig. 6 the braided metallic conductor Il has a central longitudinal passageway for the passage of fluid or the application of internal pressure which feature is common to all the embodiments for the purpose of pressurizing the spark plug or ignition conductor, or for venting gases from the spark p1ug- The system thus provides an improved appa` ratus for applying pressure to the spark plug, or for relieving pressure therefrom, according to the end which is desired. The pressurization of the magneto and ignition harness is well known, and the details of how the magneto is enclosed and pressurized do not form any part of my invention. However, the apparatus by which the pressure is transmitted from the magneto through the harness and to the spark plug eliminates many diiilculties encountered when the pressure is transmitted through airtight radio shielding; in fact such shielding is not necessary to the use of my method. Since the passageway through the ignition cable may be quite small and still transmit the required pressure, a cornplete break through one of the cables or leads as a result of gun ilre or the like. will not ailect the pressurizatlon of the other cables or leads because of the small rate at which the air can discharge through the break in the cable.

The invention may be embodied in other specic forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description,

and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

r1. In an ignition system for internal combustion engines having a source of high voltage and a spark plug including an ungrounded electrode,

an ignition cable comprising a conductor surrounded by insulation and connected between said electrode and said source, there being a passageway extending longitudinally through said cable and communicating with said electrode and said source whereby gaseous pressure may be applied to or vented Afrom said electrode.

2. A cable according to claim 1 wherein said conductor is a composite member of resistance wire and conducting rubber.

3. A cable according to claim 1 wherein said conductor comprises a composite hollow tube of conducting rubber having embedded in the wall thereof a continuous helical conductor.

4. A cable according to claim 1 wherein said conductor comprises a composite hollow conductor ol conducting braid impregnated with con- In ducting rubber.

ascuas 5. An ignition system for internal combustion engines, said system comprising: a spark plug having an ungrounded electrode; a source of high voltage; and an ignition cable connected between saidsource andsaid electrode. said cable comprising a composite hollow member of resistance wire and conducting rubber whereby fluid pressure may be transmitted through the hollow passageway in said member.

6. An ignition system for use in internal com- 10 bustlon engines for damping ouil electrical oscillations having ultra-short wavelength, said system comprising: a source of high voltage; a spark plug having an ungrounded electrode; and an ignition cable connecting said electrode to said source,

' said cable comprising a composite hollow conduc- REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,213,478 Swanson Sept. 3, 1940 2,286,233 Scott June 16, 1942 15 2,310,575 Cattaneo Feb. 9, 1943 

